Quick question about cold crashing.

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Erik the Anglophile

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Ís ok snœrs ok miðnótts boði landi frá komum
I seem to have a recurring " problem" in most of my brews, I often get yeast rafts that don't want to fall down. This has lead me to think about doing a soft cold crash, about 7-8c for two days before bottling to minimize yeast and trub in the bottles.
A few qustions: Do I need to get it back to room temp or can I bottle at that temp since will condition in room temp anyway. Do I need to plug the hole for the airlock in someway, I think because I won't bring the temp really far down, the suckback should not be that bad. And as long as I don't bring the temp up in the beer before bottling higher than it is now(~20c) I calculate the priming sugar on that temp, correct?
 

Vale71

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If you have yeast rafts that float that's probably because you used a highly flocculent yeast that was very active and formed a thick Kräusen that then kind of flocculated "in place" causing a lot of CO2 to be trapped in the yeast. This will cause the mass to have positive buoyancy and to keep floating indefinitely. I've occasionally had this happen even in conicals with some strains although even top cropping yeasts are supposed to drop completely in a conical fermenter. Unfortunately lowering the temperature is not going to fix the problem as it will actually make the rafts even more buoyant. The only way to fix the issue is to transfer in a way that will separate the yeast rafts from the beer leaving them in the fermenter. This usually means stopping the transfer somewhat prematurely and losing some more beer than usual.
 

Vale71

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Out of curiosity, which yeast strain did you use?
 

Vale71

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This matches my experience that this mostly happens with the British strains although the last time I had this happen was with Wyeast's American Ale but that's probably just a British yeast exported to the (former) colonies... ;)
 

Climb

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If it is a yeast raft that is holding trapped CO2 as Vale71 suggests, how about shaking the fermentor attempting to dislodge the floating yeast from the trapped CO2 bubbles and then doing a cold crash to help expedite the yeast settling process?
 

Bobby_M

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If gently swirling the fermenter to dislodge the CO2 bubbles holding particles up at the surface is enough to force oxygen in, I'd start with replacing the crap fermenter. If it's well sealed, there is no problem with oxygen. I've had several ounces of dry hop sludge floating up at the top that would take days to drop on its own. A quick jostling of the fermenter drops it all out and the beer could be kegged within a day. When you're trying to limit dry hop exposure to a few days, it matters.
 
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odie

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My recent Vienna lager had a huge yeast/krausen raft. I just slapped the side of the fermonster a couple times, swirled and watched it all collapse and sink to the bottom.
 
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